The invention relates to a method for performing open-loop/closed-loop control of the boosting of a braking force of a brake system, in particular of a power-assistance brake system of a motor vehicle. In addition, the invention relates to a brake booster for boosting a braking force of a brake system, in particular of a power-assisted brake system of a motor vehicle. Furthermore, the invention relates to a control unit, in particular an ABS or ESP control unit or a control unit of a brake booster by means of which a method according to the invention can be carried out, and/or a brake booster according to the invention can be open-loop/closed-loop controlled.
Activation of a brake system, for example that of a motor vehicle, is usually facilitated by means of a brake booster which increases a braking force applied by a driver of the motor vehicle by a specific amount or a specific factor, that is to say applies an additional force. A resulting total force or braking force is conveyed to the brakes of the motor vehicle, which subsequently brake one wheel or a plurality of wheels of the motor vehicle. A widespread type of brake booster operates on the basis of a partial vacuum accumulator which is evacuated by a suction port of an internal combustion engine of the motor vehicle, with the result that the partial vacuum accumulator makes available energy for boosting the braking force. Not every motor vehicle has an internal combustion engine which can be used to evacuate the pressure accumulator. For example, this is used in diesel vehicles or electric vehicles by way of example instead of using an electrically operated partial vacuum pump. However, partial vacuum accumulators and brake boosters which are based thereon are bulky and the arrangement of the brake booster with respect to the brake system therefore has little flexibility.
DE 10 2007 016 863 A1 discloses an electromechanical brake booster for a motor vehicle, having a rotationally symmetrical cam mechanism roller which is driven by an electric motor. The cam mechanism roller has a pitch groove by means of which a pickup can be moved linearly to and fro on a longitudinal end of a lever during operation of the electric motor. At a longitudinal end of the lever opposite the latter, said lever is connected to a piston of a master brake cylinder and can thereby transmit a force, resulting from the electric motor to the piston. In a center region, the lever is mounted in an articulated fashion, wherein a length ratio of the pickup to the center joint and of the center joint to the mechanical connection to the piston sets a lever ratio of the brake booster. In the case of a method for operating the brake booster, the lever, the cam mechanism roller and therefore the pitch groove and a shaft of the electric motor always have the same position with respect to a specific position of the piston, with the result that an available transmission ratio cannot always be used in an optimum way.